Basal replication of hepatitis C virus in nude mice harboring human tumor

An overview of mouse models of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) has become a severe burden on global health due to its high morbidity and mortality rates. However, effective treatments for HCC are limited. The lack of suitable preclinical models may contribute to a major failure of drug development for HCC. Here, we overview several well-established mouse models of HCC, including genetically engineered mice, chemically-induced models, implantation models, and humanized mice. Immunotherapy studies of HCC have been a hot topic. Therefore, we will introduce the application of mouse models of HCC in immunotherapy. This is followed by a discussion of some other models of HCC-related liver diseases, including non-alcoholic fatty liver disease (NAFLD), hepatitis B and C virus infection, and liver fibrosis and cirrhosis. Together these provide researchers with a current overview of the mouse models of HCC and assist in the application of appropriate models for their research.

Development of Humanized Mice for the Study of Hepatitis C Virus Infection

The development of a small animal model for hepatitis C virus (HCV) infection is a critical issue for the development of novel anti-HCV drugs. To this aim, we have tried many different approaches for generating mice carrying humanized liver. Main efforts were focused on the transplantation of human hepatocytes into immunocompromised mice (SCID-/-, Bg-/-) carrying a genetic lethal liver disease (Alb-uPA). Survival of homozygotic animals should largely depend on early transplantation with healthy hepatocytes. In parallel to establishing a colony of Alb-uPA/SCID/Bg mice, we developed a microsurgical procedure for intrasplenic xenotransplantation of healthy hepatocytes in 1-week-old mice. So far, we generated several chimeras by xenotransplanting human hepatocytes in Alb-uPA+/+/SCID-/-/Bg-/- mice at 1 week after birth. In a first step, identification of successfully engrafted animals is possible by quantification of human serum albumin and human alpha 1 antitrypsin in mouse sera. Additional preliminary histomorphological analysis of liver sections from chimeric animals was also carried out. One of the mice was transiently infected with HCV, reaching viremia levels of approximately 10(5) genomes/mL. However, the efficiency of this system to generate chimeric mice is still very limited. We are currently exploring the use of more robust models of hepatic disease. Moreover, we have been also exploring novel strategies for the generation of chimeric mice by xenotransplanting human adult stem cells, instead of human hepatocytes, at preimmune stages of development.

An in vitro model of hepatitis C virion production

The hepatitis C virus (HCV) is a major cause of liver disease worldwide. The understanding of the viral life cycle has been hampered by the lack of a satisfactory cell culture system. The development of the HCV replicon system has been a major advance, but the system does not produce virions. In this study, we constructed an infectious HCV genotype 1b cDNA between two ribozymes that are designed to generate the exact 5' and 3' ends of HCV. A second construct with a mutation in the active site of the viral RNA-dependent RNA polymerase (RdRp) was generated as a control. The HCV-ribozyme expression construct was transfected into Huh7 cells. Both HCV structural and nonstructural proteins were detected by immunofluorescence and Western blot. RNase protection assays showed positive- and negative-strand HCV RNA. Sequence analysis of the 5' and 3' ends provided further evidence of viral replication. Sucrose density gradient centrifugation of the culture medium revealed colocalization of HCV RNA and structural proteins in a fraction with the density of 1.16 g/ml, the putative density of HCV virions. Electron microscopy showed viral particles of approximately 50 nm in diameter. The level of HCV RNA in the culture medium was as high as 10 million copies per milliliter. The HCV-ribozyme construct with the inactivating mutation in the RdRp did not show evidence of viral replication, assembly, and release. This system supports the production and secretion of high-level HCV virions and extends the repertoire of tools available for the study of HCV biology.